Securing devices of the above kind, which form in general a fastener of a rivet-like kind, have been proposed in the past. These prior art devices comprise an expandable boss or grommet which extends through the members which are to be assembled together, and through which there extends a fixing screw which is screwed into an expander nut. The expander nut cooperates with the free, split end of the expandable boss, in such a way as to dilate the end wall of the latter behind the support plate, so as to fix the said member against the support plate by an axial clamping action. This type of device is for example described in U.S. Pat. No. 3,911,782. Lateral adjustment of the said member in all directions in a plane with respect to the support plate may be made possible by providing a predetermined clearance within the hole that is formed through the support plate, and through which there extend, in particular, the expandable boss and the fixing bolt.
By contrast, axial adjustment of the distance between the said member and the support plate, in a direction perpendicular to the said plane, can only be made possible by inserting one or more spacing rings or shims, which complicates the operation of assembling the member into position.